Casement window assemblies are generally well known in the art. A casement window typically includes a window sash having a glass assembly surrounded by wood, vinyl or metal structure disposed in a frame with a central opening. Operable casement windows typically have the sash hinged at one side between an upper and lower hinge assembly. These assemblies enable the window to pivot between them at one side so the window may swing outward from the frame. An operator mechanism is usually attached to the lower hinge for selectively opening and closing the window sash. Casement windows are frequently used in all manner of installation locations due to their convenience, ease of use, and relative airtightness compared with sliding window designs.
Over the years, the market has demanded continually increasing window performance, including reduced window air infiltration. Typically, casement windows are designed with a stop frame structure disposed inward of the sash, against which the sash seals when the window is closed. Windows on the downwind side of a structure are subjected to negative pressure—that is, the pressure outside the structure is less than the pressure inside the structure, tending to draw the sash away from the stop frame against which it is sealed. A locking mechanism present along the lateral edge of the sash and the hinges at the top and bottom of the sash are relied upon to hold the sash in place. On the pivoting edge of the window opposite the locking mechanism edge, hardware known as snubbers are used to retain and stabilize the sash against negative pressure. One example of such negative pressure window snubber is disclosed in U.S. Pat. No. 5,742,978.
Snubbers generally function in one of two different ways: (1) a “compression snubber” causes the weatherstripping to be compressed by a desired amount and holds the sash in an optimum position against the weatherstripping to assure a sealed window; or (2) an “interlocking snubber” has features (generally hooks) that engage when the sash is exposed to high negative air pressure and prevent the snubbers from sliding past each other as the sash bows outward. A drawback of past interlocking snubber designs, however, is that there is significant clearance between the snubber components when the window is in the closed position in order to avoid interference when the window is operated. Hence, while they are generally effective for preventing excessive bowing of the sash under high negative pressure, this type of snubber does not provide the sealing performance of a compression snubber. Consequently, a higher than desired amount of air infiltrate through the assembly when the window is in its closed position.
What is needed in the industry is a window assembly having improved integrity and design capabilities when the sash is subjected to negative pressure and which provides a tighter seal between the seal and frame to inhibit air infiltration.